Hydrological modeling of green infrastructure to quantify its effect on flood mitigation and water availability in the high school watershed in Tucson, AZ

Authors: KORGAONKAR, Y. - University Of Arizona; GUERTIN, D.P. - University Of Arizona; MEIXNER, T. - University Of Arizona; Goodrich, David - Dave

Submitted to: International Society for Photogrammetry and Remote Sensing Proc
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2021
Publication Date: 6/29/2021
Citation: Korgaonkar, Y., Guertin, D., Meixner, T., Goodrich, D.C. 2021. Hydrological modeling of green infrastructure to quantify its effect on flood mitigation and water availability in the high school watershed in Tucson, AZ. International Society for Photogrammetry and Remote Sensing International Journal of Geo-Information. 10(7):443. https://doi.org/10.3390/ijgi10070443.
DOI: https://doi.org/10.3390/ijgi10070443

Interpretive Summary: Urbanization has a profound influence on watershed hydrology by increasing runoff volumes and peak runoff rates. Incorporation of green infrastructure (GI) into developments such as infiltration gardens, rainwater harvesting cisterns, and permeable pavement is gaining acceptance as a measure to reduce post-urbanization runoff. The Automated Geospatial Watershed Assessment (AGWA) Urban tool was developed to simulate the hydrologic behavior of built environments that incorporate GI using the Kinematic Runoff and Erosion (KINEROS2 or K2) model. The K2 model provides an urban modeling element that can be used to represent various land cover types and GI. This study models the 3.31 km2 High School watershed in Tucson, Arizona in which each parcel in the watershed was individually represented using the K2 Urban element. Seven GI configurations were simulated using large design storms and 20 years of simulated rainfall data to understand the effects of GI on flood mitigation and long-term water availability, respectively. The design storm analysis indicates that the current level of GI implementation (175 on-street basins and 37 roof harvesting cisterns), has minimum (<2%) influence on runoff volume. When the GI features were increased by a factor of two and five, a larger reduction of peak flow (<8% and <22%, respectively) and volume (<3% and <8%, respectively) was simulated. The 20-year analysis showed that parcels with roof runoff harvesting cisterns were able to meet their landscape irrigation demands 10 months out the year. The current level of GI implementation in the High School watershed may not have significant large-scale impacts, but it provides numerous benefits at the parcel, street, and small neighborhood scales.

Technical Abstract: Green Infrastructure (GI) practices are being implemented in numerous cities to tackle stormwater management issues and achieve co-benefits such as mitigating heat island effects, as well as water augmentation, health, and economic benefits. In Tucson, Arizona stormwater is routed along the streets to the nearest ephemeral washes. Local organizations have implemented various GI practices, such as curb cuts, traffic chicanes, roof runoff harvesting, and retention basins, to capture the excess runoff and utilize it on-site. This study models the 3.31 km2 High School watershed using the Automated Geospatial Watershed Assessment tool and the Kinematic Runoff and Erosion (KINEROS2 or K2) model. Each parcel in the watershed was individually represented using the K2 Urban element. Seven GI configurations were simulated using design storms and 20 years of stochastically generated rainfall data to understand the effects of GI implementation on flood mitigation and long-term water availability, respectively. The design storm analysis indicates that the configuration designed to mimic the current level of GI implementation (175 on-street basins and 37 roof harvesting cisterns), has minimum (<2%) influence on runoff volume. When the GI implementation was increased by a factor of two and five, a larger reduction of peak flow (<8% and <22%, respectively) and volume (<3% and <8%, respectively) was simulated. The 20-year analysis showed that parcels with roof runoff harvesting cisterns were able to meet their landscape irrigation demands 10 months out the year. The current level of GI implementation in the High School watershed may not have significant large-scale impacts, but it provides numerous benefits at the parcel, street, and small neighborhood scales.